1. Field of the Invention
This invention relates to mechanical mountings for objectives, and more particularly to the adjustment of the axial position of an intermediate sleeve having a guide portion for controlling the movement of a lens component relative to the fixed tube or the focal plane in the camera body so that the focusing position for infinity of the objective relative to the camera body is rigorously determined. Still more particularly it relates to a mechanism for adjusting the axial separation between two of the lens components of the objective which enables the adjusting operations on the assembly line to be carried out very easily, while permitting a high precision accuracy lens mounting to be achieved.
2. Description of the Prior Art
To assure high precision accuracy of imagery of a camera, the mounting of the multi-component objective in the barrel necessitates highly accurate spacing adjustments. In addition thereto, it is of great importance to adjust the axial position of the objective relative to the camera body with high accuracy as the body tube of the lens mounting is manufactured to a lower degree of tolerance than necessary. The process for performing these adjusting operations is very complicated, and the prior known adjusting techniques have not enabled higher precision accuracy lens mounting mechanisms to be realized.
FIG. 1 is a longitudinal section view in an upper half of the prior known zoom lens mounting mechanism for use with a camera body. A body tube 1 has a mount for coupling with the camera body at the rear end thereof. An intermediate sleeve 2 is first movably fitted in the inner diameter of the body tube 1 and, after its axial position has been adjusted by using a washer 7 of appropriate axial length, is then fixedly secured thereto by a screw fastener 8. A sleeve 3 is movably fitted in the inner diameter of the intermediate sleeve 2 and is connected to an actuator ring 6 which is rotatable and axially movable relative to the body tube 1. Lens holders 4 and 5 are movably fitted in the sleeve 3 by screw-threaded and cam means respectively. The process for re-adjusting the position of the zoom lens relative to the camera body comprises the steps of: (1) taking off the fastener screw 8, (2) disassembling the intermediate sleeve 2 out of the body tube 1, (3) exchanging the spacing adjusting washer 7 with one of required length, and (4) re-assembling these parts with the body tube. Since the washer 7 is used for absorbing the accumulative error due to the tolerances to which the lens components and the holders therefor are produced, for the error is different with a different lens mounting item, there is a need to provide a large number of washers of different axial length. Also, because this length varies discretely, it is difficult to achieve fine adjustment.
As will be seen from the foregoing, the prior known spacing adjusting techniques necessitate very elaborate work. Also, despite the fact that the spacing should be held to a high degree of tolerance, since the adjusting thereof can only be performed in discrete values, a much-desired increase in the accuracy of the lens mounting mehchanism has so far not been achieved.